Cooling towers: Not solar powered, just using
water to cool the incoming air. Exhausting the hot air can be solar assisted,
however, via a vent chimney.

Solar Refrigeration: Doesn't cool when the sun
shines, but the energy is used to dry out an adsorbing media (zeolite) which
then re-absorbs water evaporated by the load (refrig) at a lower than normal
temperature due to being held in a partial vacuum.

Another natural form of air conditioning / ventilation
is to use the solar heat to evacuate the hot air from a house, and
cause cool air to be drawn in from an earth tube. Note that the cooling effect
is actually provided by the thermal mass of the earth around the tube; the
sun is simply pumping the air. This technique was used or
invented by the Romans a long time ago.

A trench 6 to 12 feet deep and 100 to 200 yards long was
dug leading from the "house" in a straight line away from the house.

Into this trench a large diameter pipe (these days corrugated
drainage pipe 2 or 3 feet diameter) was laid, with holes drilled into the
bottom to drain water that condensed inside the pipe. The trench was then
covered over.

At the far end a 90 degree elbow was attached and more pipe
added so that it reached above ground and the end covered with some sort
of wire mesh attached to keep out unwanted things such as rodents, etc.,
and then another elbow could be added at this end to shield against
rain.

The house end of the pipe entered the house and was the
source of incoming air.

The key to making this work is to add a convection
chimney.

The Convection chimney is built such that it's inside opening
is at a high point inside the building.

On the outside, two intersecting sides of the chimney; are
painted flat black, and the resulting V formed by the two connecting sides
face south. In other words, the V needs to face the mid point between where
the sun rises and sets.

The two other sides must be transparent, Plexiglas or some
equivalent. Also, the higher/larger the chimney, the better.

How it works: the sun heats up the chimney causing the air inside
to rise, thus drawing air through the cool pipe. The pipe cools the air drawn
from the outside to the temperature of the earth at the depth at which it
is buried (which is virtually constant year around at this depth). By the
way, an interesting note: Even in cold climates where the ground is frozen,
the incoming air is only 32F when the air outside may be much colder, we
need only heat the air by 38F to bring it to 70F; as opposed to heating outside
air of say -15F to 70F we would have to heat the incoming air by 85F - quite
a difference in the amount of heating energy we would have to supply by some
other means.

Of course, without the sun to warm the chimney (or some
other source) the system isn't worth fooling with. Other possible
replacements for the chimney are
Whole
House Fans.

A few points:

1. Surface area, NOT size. It does no good to dig a 10 foot diameter tunnel
since the air in the center is insulated from the cooling effect of the tunnel
wall.

2. Maintenance will be required. Animals, weeds, roots and all other manner
of bad things will happen.

I would (have not yet) find an area near the space to be cooled which slopes
away (for drainage) and then dig a pattern of deep pits, like fox holes.
I would then use an auger to dig horizontally (slightly down slope) between
the pits and line the holes with sections of metal pipe assembled in the
pits. The pits would then be covered with an insulating material which can
easily be removed to allow access to the pipe segments for cleaning or clearing
with a rag tied to the top of a flexible pole.

The ideal landscape in which to install such a system would be a something
like the side of an overturned bowl. Imagine cooking a chocolate cake in
a shallow bowl, then emptying it out onto a platter. Built your house at
the top and then cut small pie shaped sections every few inches around the
cake, but remove only the top half of each cut section and then only back
into the mound a short distance. Now, push soda straws between the cut out
sections, near the bottom of the cut so that they are linked around the side
of the mound. Remove all but the shell of the sections you cut out and use
them to cover the openings so that the ends of the straws are still open,
but the air will not be able to leave the overall straw system. At the end,
use a bendable straw to direct the air up to the house on top and the solar
tower.

If you can't find that terrain, you might be able to get away with long metal
tubes, very gently curved and buried with a ditch digger so that both ends
are above ground. Small drainage holes will need to be drilled along the
lowest point of the pipe and gravel or other darning system installed at
the bottom of the ditch before the pipe is laid in. Connections between pipe
segments would be made with a manifold or other plumbing above ground and
should be well insulated. Cleaning or maintenance would require the disassembly
of the manifold so some form of normally covered opening on the opposite
side of the manifold from each pipe could be a very helpful addition. Easy
to install, maintain and provides a large surface area of contact between
the ground and the air.

At the worst, if you can dig any sort of a ditch and connect both ends of
the buried pipe back into the home, you can run a rope through the pipe to
form a loop. Sponges, towels or other cleaning devices can be attached to
the rope and then pulled through the pipe. As long as the rope doesn't break...

How to stay cool in the hot desert (cooling tower) HomePower Magazine #41,
June 1994

A good idea:

Why not combine a chimney and a cooling tower?
One outer shell of thermally transparent material, inside that, a heat exchanger
to transfer radient solar energy into the air, then an insulative layer and
finally, a cooling tower with some combination of water mist, evaporative
pads, or thermal conductors driven into the ground.

I had a crazy idea some time ago, about using a small, cheap solar collector
to produce superheated steam (and my father and I did build the device described
up to this point and it worked just fine) and then use a venturi to trade
the velocity of escaping steam for volume of air moved (inject steam via
a fine pitot into the opening of a pipe so that outside air is pulled into
the pipe) [ed: better yet, use the steam jet to create a vacumn in the exit
pipe on the hot side and avoid the temp increase of the steam on the inlet
side] and then direct that into a Hilsch Vortex
tube to produce hot/cool air for house A/C.

I would guess that back pressure at the entrance to the Vortex would limit
the incoming air volume excessively or that the increased temp of the air
(due to the steam injection) would negate any cooling gains on the part of
the Vortex or some such other problem would prevent it from working. The
nice thing would be: No moving parts other than the water and the air and
the collector (sun tracking), automatically starts when the sun heats it
up, super low construction cost, almost zero operating cost (only maintenance
and water supply). The potential inefficiencies are offset by the low (zero)
cost of water and sunlight.

Russell McMahon commented:

Use of steam for refrigeration was a standard technique early this century.
AFAIR, steam was expanded through a nozzle and drew air from a venturi tube
(?) creating a low pressure region with accompanying cooling. Old or complete
air conditioning books would cover this - I have only seen it described once.

The advantage is, as you note here, that you can convert available thermal
energy into cooling. Also, there are no moving parts. You could also consider
using a "kerosene fridge" type arrangement which uses heating to drive an
adsorption cycle using, typically, ammonia and water. Only moving parts here
are the fluid(s). This may be easier as the technology is current and common
and you could copy an existing fridge or use an existing one and simply heat
the appropriate point.

Steam-jet refrigeration is still used to concentrate fruit juices and similar
temp sensitive substances. There is a Scientific American article about
construction of a Vortex tube, circa late '50s, early 60's... Mo' high-tech:
http://www.sunpower.com

Annie Ogborn says:

...Randy Hees at
Ardenwood
Historic Farms
(infoseek
search results) in [Fremont near] Newark, CA. The farm and the Society
For the Preservation of Carter Railroad Resources are some of the most
knowledgeable people in the country about obsolete technologies. Randy Hees
is pres. of SPCRR.

Another good resource is the
Society for Industrial
Archeology's skills preservation section. [see vol. 16 no 1 for "Artificial
Refrigeration and the Architecture of 19th-Century American Breweries," Susan
K. Appel, 16, 1(1990):21-38]

Russell McMahon describes another system that he has uncovered...

It relies on what is termed an "ejector" or "steam ejector" or a thermodynamic
compressor. These terms are in fairly standard use.

Steam from a highish pressure source is expanded through a diverging nozzle
and then run on through a longer converging section. The pressure drops in
the initial section and then rises again to a lower level. At the lowest
pressure point (at the end of the initial expansion section) a hole is placed
which enters into a chamber.

The result is to lower the pressure of the attached chamber and entrain any
vapour from this chamber into the expanding and contracting steam. The drop
in pressure in the chamber causes vaporisation of the water in the chamber
to produce cooling.

Systems I have seen described recently said that a steam pressure of about
10 bar is typically used and that the steam vaporised is about 20% of the
total vaporisation. ie about 4 times as much vapour is derived from the chamber
as comes from the steam boiler.

I have mentally designed a really cheap solar collector using concrete, re-bar,
hose clamps, a huge stack of razor blades, a small compressed air tank, sheet
metal and the 1 foot square decorator mirrors found at any home supply. Tools
are: two steel pins cast in concrete to use as a re-bar bending tool, a bench
vice with the jaws widened by a pair of steel bars to bend the sheet metal,
a cut off tool (air or electric drill powered), and the normal screwdriver,
etc... Several lengths of re-bar are bent like:

__ __
| |______________| |

The ends are sharpened to a chisel point (cut off tool) and rest in groves
on concrete pads at either end. Attach guy wires from the center span to
the high points to prevent flexing, but do that after the mirrors are mounted.
They will now rock side to side with little pressure. A connecting rod is
fashioned to connect the high points on one end or the other together so
that an actuator may position the array to point to the sun. The sheet metal
is cut into strips about 6" wide and 18" long and bent into the following
shape:

_ _
\ /
\^/

with a small slot cut near the bottom of the lower bend for the hose clamp
to pass through. They are clamped along the re-bar. Spread the top open,
insert a decorator mirror and let go. This clamps the mirror. Loosen the
hose clamp, align the mirror holder so that all the mirrors point back to
a common point centered above the collector.

At this focal point, rests a boiler on a mast of two pipes (water in, steam
out).

Bolt the stack of razors together with two long very high test bolts. Use
big very high test washers on either end. Vice them so that the edges are
PERFECTLY aligned. Tighten them with breaker bars till you are sweating and
the heads and nuts round off then tighten them some more. Smooth any
irregularities along the sides of the stack.

Cut a slot in the end of the air tank just the width of the stack of razor
blades and cut two holes for the pipes and one for a pop-off valve. Take
the blades, pipes, and tank to your local welding shop and challenge them
to weld the stack into the slot (I know it can be done, I've seen it, wrapping
the stack in super thin steel foil helps) and the pipes into the holes so
that one is almost to the top and the other is near the bottom. Also weld
on the pop-off valve (a mother big chunk of steel with a 1" hole in one end
that rests over a short length of pipe with a cap that has a small hole in
it; remember pressure cookers?). Pressure test the boiler professionally.
This boiler will work very well. Nothing transfers heat into water like a
stack of razor blades.

We need a small (very high pressure) water injection pump, a sun tracking
actuator, and maybe a better pop off valve. I can't remember how the injection
pump knows when the boiler needs water.

how much degrees does an ejector cool the water in a steam ejector refrigration
system?+Darn fine question. There just isn't
enough documentation available to answer it.

I'm looking at buying
a home with a dirt basement on a city lot, so I don't have 200 yards of ground
to put pipe in. However, it does have a dirt basement. Is there anything
that says the pipe has to be straight AND not underneath the house? Could
I curl it around in a spiral underneath my basement's dirt floor and have
the far end duck under the foundation and come up just outside the
house?
James
Newton replies: For cooling tubes, you want as much surface area surounded
by as much earth as possible. So the ideal configuration is a lot of tubes
radiating deep into the mass of the earth. And since the air temperature
in the tube will reach the air temperature of the earth fairly quickly with
a low volumn of air flow, you don't need that long a tube unless you are
pulling the air through quickly, which takes more energy and is therefore
less efficient.

Another issue is one of condensation and moisture in the pipe. That can lead
to mold and serious health problems. To prevent it, the air inlet
of the tube must be at the low point and there has to be a steady slope all
the way down so the condensate can drain. This is hard to ensure with a coiled
pipe.

In your case, it would be easier just to vent from your basement up into
the house. The air between the house and the earth is probably several degrees
cooler.+

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